1. Field of the Invention
The present invention relates to an improved technology for a pivot shaft structure used for making a vehicle body frame support for a swing arm.
2. Description of Background Art
In a motorcycle, a rear wheel is attached to a vehicle body frame via a swing arm for mounting the rear wheel to the vehicle body frame so as to be capable of swinging in the vertical direction. A pivot shaft is an element used for connecting the swing arm to the vehicle body frame.
In the related art, it is known that a locknut is used for a pivot shaft of a motorcycle. See, for example, JP Patent No.2564078 (FIG. 1).
FIG. 16 is a drawing that is disclosed in JP Patent No.2564078. However, the reference numerals are renumbered.
A pivot shaft structure is configured by mounting a boss 104 as an outer cylinder to, and integrating with, a sleeve 101 as an internal cylinder via needle bearings 102, 102 and a ball bearing 103. The structure is placed between left and right frames 105, 106. A pivot shaft 107 is set by screwing it through the left frame 105 into the left frame 105 through the sleeve 101 and into the frame 106. A nut 108 is secured onto the pivot shaft 107 at the right end in the drawing. A locknut 110 is screwed onto the pivot shaft 107 at the left end in the drawing.
This structure exhibits an effect of preventing the idling of the running of the pivot shaft 107 with respect to the frame 105 by screwing the locknut 110 onto the pivot shaft 107.
The locknut 110 is a nut having four notches 111 . . . ( . . . represents a plurality of elements, hereinafter) on the outer periphery thereof. Although its shape is rather specific, it is a component which is often employed.
However, in order to fasten the locknut 110, it is necessary to provide a specific tool 114 having four claws 113 . . . at the extremity of a cylindrical portion 112, and engage the claws 113 . . . with the notches 111 . . . . The specific tool 114 having the plurality of claws 113 . . . has a significant cost.
In addition, since it is required to use the specific tool for the locknut 110 in the related art, torque control is difficult, and hence a number of steps are required for torque control.